Resource allocation for multicast services in multicarrier wireless communications

In multicast wireless communications, the difference in link conditions of users due to fading limits the capacity of multicast data. In this paper, we confirm this by proving that in wireless fading channel, multicast capacity is saturated as the number of users increases. However, if we assume that the multicast data are separated into layers and any combination of the layers can be decoded at the receiver, the network throughput can be increased by performing subcarrier/bit allocation. In this paper, we develop the optimum subcarrier/bit allocation methods for not only maximum throughput (MT) but also proportional fairness (PF) by employing integer programming (IP) which is NP-hard problem. To reduce the complexity, suboptimum two-step algorithms are also proposed separating subcarrier allocation and bit loading. Numerical results show that the proposed resource allocation schemes for both MT and PF significantly outperform the conventional multicast transmission technique depending on the lowest channel gain. Additionally, it is shown that the performance difference between the optimum and suboptimum algorithms for both MT and PF is within about 5%.